Eliminating The Low Oil Pressure Gremlin - Engine Builder Magazine

Eliminating The Low Oil Pressure Gremlin

Whether you’re a Production Engine Remanufacturer (PER) or a Custom Engine Builder (CER), this issue has shown up in your
warranty or complaint area like the nasty gremlin that it is. So let’s
go on a journey and see what you think.

"Low Oil Pressure" is the frightening gremlin of which I speak! Here is
the situation: your customer just got his vehicle back with your newly
remanufactured engine. But wait: as he returns home, as far as he can
tell there is either no more – possibly less – oil pressure than the
old engine had. Or, perhaps they notice that dreaded hot idle oil light
flicker, even though the engine meets the minimum pressure allowed by
the OE.

What does the innocent consumer believe? Defective workmanship, trying
to get away with something, taking short cuts – no matter what the
reality is, they feel like you’re taking advantage of them!

Even though every component was machined to exacting specifications and
tolerances, this problem rises up and grabs you like a mad pit bull
with a death grip on your throat (see Tom Hanks in the movie "Turner
and Hooch"). In more instances than I like to hear about the engine is
replaced with another and everything appears to be fine.

Once the engine in question is returned, all kinds of diagnostics then
take place, from oil bleed testing to complete disassembly and
re-measurement of all of the components. Oil pump and pick up testing
is conducted. Cam bearing oil hole locations are examined, yet
invariably, nothing stands out as being a problem.

The components from that engine may be put back into the system and
never see each other again as a complete unit. Yet none of the
components are ever identified as a problem for any other assembly.

So how do you explain the oil pressure gremlin? More often than not you
can’t, and you just move on to "it happened" and that is that.

I can’t give you a foolproof solution but how about one that has been
extremely helpful in eliminating the oil pressure gremlins from many an

Before I give you that however, let’s take a quick moment to talk about
what happens at the OE level when an engine is assembled. There was a
time when the words "select fit" was limited to import engine
applications and it allowed them to install select fit engine bearings
that were slightly larger and smaller in size so that the optimum
minimum bearing clearance could be obtained on each individual
crankshaft journal be it connecting rod or main bearing. Well that
procedure exists in nearly every engine application being assembled
worldwide today.

Regardless of how stringent the procedures and quality control are on
the remanufacturing side, the use of select fit bearings is neither
feasible, economically sound or even available in undersize bearings.

But rising up again, as if from the dead, is the undying
entrepreneurial spirit of the "engine builder." What do I mean by that?
It’s no trick – and for many situations they’re proving to be the
perfect treat: main bearings that seem to completely eliminate the low
oil pressure issue.

No, they are not some voodoo magic but they are a way to address and
combat the possible low oil pressure issues described above. What
exactly are they? They are main bearings in which the oil grove is
terminated prior to getting to the parting line.

As you’ll see in Figure 1, the oil groove terminates before it gets to
the bearing parting line. This style of main bearing has accounted for
a 15 percent or more increase in hot idle oil pressure. So if you’re
looking to eliminate some of those unexplained low oil pressure
gremlins contact your bearing manufacturer and ask about this style
bearing and availability for the engine applications that you are

A special note of thanks goes out to the engineering people of
ProFormance Engines, Springfield, MO, and in particular Reggie Gray.
Figure 1: Note the difference in the oil groove of the top bearing terminating prior to getting to the bearing parting in the lower bearing.

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